Add typeahead dropdown for team selection in match play

[horner]

Replace the plain number input for team selection on the match play page with a typeahead text input backed by a datalist of all event teams. This lets operators type a team number or name to filter suggestions, or browse the full dropdown list.

Showing a dropdown from the team list.

Changes:

• web/match_play.go: Fetch all teams from the database and pass them to the template.
• templates/match_play.html: Replace input type=number with input type=text list=teamList and add a shared datalist populated with all teams (ID + nickname).
• static/js/match_play.js: Update getTeamNumber() to robustly parse team IDs from the text input.

Test notes:

• go test ./web/ -run TestMatchPlay passes.
• go build succeeds.
• Verified in browser: dropdowns show teams, type-ahead filtering works, substitute teams flow works.